This application is related to and claims priority from Japanese Patent Application No. HEI 2000-108,326, which was filed on Apr. 10, 2000, the entire contents of which is hereby incorporated by reference.
1. Field of the Invention
The present invention generally relates to dampers for vehicular suspension systems. More particularly, the present invention relates to dampers configured with an internally moveable component to reduce the effects of small scale, rapid movements upon the vehicle.
2. Description of the Related Art
Vehicles are provided with suspension systems to reduce the effects of bumps and irregularities in the surfaces over which they are operating. The same suspension systems act to place the wheels or other suspended members (i.e., skis and the like) in firm contact with the operating surface such that operator control can be increased.
The suspension systems often comprise hydraulic dampers that are interconnected in any of a number of manners. The hydraulic dampers generally comprise a cylinder further comprising a first chamber and a second chamber with a fluid connection extending through a piston that divides the first chamber from the second chamber. The cylinder is often connected to either the frame of the vehicle or the suspended member (i.e., the wheel, the ski or the like) while the piston is connected to the other.
For illustrative purposes, the cylinder can be connected to the vehicle""s frame while the piston is connected to the wheel. When the wheel moves downward relative to the vehicle frame, the piston and the cylinder move such that the unit lengthens. Due to this movement, the movement of the piston reduces the volume in the first chamber and increases the volume in the second chamber. The fluid within the first chamber, thus, is displaced through valves that control flow through the fluid connection between the first chamber and the second chamber. The valves restrict the flow to some degree. When the wheel moves upward relative to the vehicle frame, the piston and the cylinder move such that the unit contracts. Due to this movement, the movement of the piston within the cylinder reduces the volume in the second chamber and increases the volume in the first chamber. Once again, fluid is displaced through valves positioned in the piston and the movement is damped by the restricted flow.
The restricted flow and damping action is controlled by the type of throttling employed by the valves between the chambers. To create a large damping force, a first type of valve is required that decreases the flow rate (i.e., a stiff suspension) and, to create a small damping force, a different type of valve is required that increases the flow rate (i.e., a soft suspension). If the suspension system is configured to be stiff (i.e., the flow rate is decreased) then relatively small bumps are easily transferred to the vehicle frame from the wheels. Of course, if the suspension system is configured to be soft (i.e., the flow rate is increased) then the vehicle will operate between the bump stops of the suspension components, which adversely impacts longevity of the components.
Accordingly, a suspension damper is desired that can provide stiffer action to reduce the larger ranges of movement caused by larger bumps while suitably absorbing smaller ranges of movement caused by smaller bumps.
One aspect of the present invention involves a damper for a suspension system. The damper comprises a cylinder body with a moveable wall disposed within the cylinder body. The cylinder body comprises an outer wall and an end cap with the end cap enclosing a first end of the cylinder. A first chamber is at least partially defined by the outer wall and the moveable wall and a second chamber is at least partially defined by the outer wall, the end cap and the moveable wall. An axially moveable member is positioned within a portion of the second chamber and a compressible member is disposed generally between the moveable member and the end cap. The compressible member has one surface generally fixed in an axial location relative to the end cap.
Another aspect of the present invention involves a hydraulic damper comprising a cylinder body with a piston reciprocal within the cylinder body. A first chamber is defined on a first side of the piston and a second chamber defined on a second side of the piston. The piston comprises at least one passage connecting the first chamber and the second chamber. A pressure-responsive valve regulates flow through the at least one passage. A piston rod is connected to the piston and extends through an end of the cylinder body. A disk is positioned between the end of the cylinder body and the piston. The disk also interposed between a stop and the piston with a compressible member being interposed between at least a portion of the disk and the stop.